1. Field of the Invention
This invention relates generally to apparatus for repairing and refurbishing the bearing surfaces of rotating shafts of large machines at a job site, and more particularly to a portable journal turning lathe that can be readily transported to a location in the field where a machine is to be repaired, mounted in place on the machine's shaft to be turned and then operated to remove any scoring and other surface irregularities from the shaft so that it is ready for replacement of its bearings.
2. Discussion of the Prior Art
In my earlier U.S. Pat. No. 5,660,093 I describe a portable journal turning lathe that comprises a pair of split clamshell assemblies that are held in parallel, spaced relationship by a plurality of spacer rods, two of which support a tool carrier assembly for axial movement relative to a shaft to be turned by the lathe. The tool carrier assembly includes at least one, but preferably two, cutting tool advancing mechanisms for controlling the radial position of the cutting tools and, hence, the depth-of-cut. The tool carrier assembly is arranged to be reciprocally driven in the axial direction by a threaded lead screw, driven by a star wheel which rotates through a predetermined angle upon each full rotation of the clamshell's movable ring member. The lead screw operates with a quick-release nut in the tool carrier assembly to permit rapid return of the tool carrier assembly to a home position upon completion of a pass.
In this earlier arrangement described in my '093 patent, the entire assembly including the guide rods 38 and 40, the tool slide block 46 and the cutting tool carriers 56 and 58 along with the counter weights including stabilizer brackets 28 and 32 and the spacer rods 42 and 43 all orbit the shaft to be turned as the ring gear 22 of the clamshell assembly 16 is driven. As such, in close quarters where the shaft to be turned is close to other stationary objects, there have been applications where that device could not be used because of the relatively large diameter of the sweep of outwardly projecting structures, such as its tool adjustment knobs 62. It was also found somewhat difficult to hold tolerances, given the change in the center of mass of the spinning structure as the tool carriage assembly 46 traversed its longitudinal path of travel.
In the journal turning lathe of my earlier '093 patent, a certain amount of difficulty is encountered in efforts to properly concentrically mount the clamshell assemblies relative to the shaft to be turned so that the support rails 38, 40, 42 and 43 will extend parallel to the shaft to be turned. It might typically take about two hours to install the journal turning lathe of the '093 patent on the shaft.
Still another drawback of my earlier design resides in the fact that the length of longitudinal travel of the tool slide block 46 is limited by the distance between the clamshell assemblies on each end of the guide rods. With this arrangement, it was not possible to turn the shaft all the way to a shoulder on a shaft or to its free end because a certain shaft length proximate its free end had to be used for mounting one of the pair of split clamshell assemblies to the shaft.
The journal turning lathe of the present invention obviates each of these drawbacks. Rather than having a pair of split ring clamshell assemblies at each end thereof, my present invention employs a pair of stationary clamping rings that are adapted to be centered at spaced-apart locations along a length of the shaft to be turned and extending between the clamping rings are a plurality of elongated, cylindrical glide shafts. A split ring clamshell assembly of the type having a stationary ring and a movable or rotatable ring journaled to the stationary ring is slidably supported on the plurality of glide shafts. Separate motors are provided for rotating the movable ring on the clamshell lathe assembly and for translating the clamshell lathe assembly longitudinally along the glide rails between the clamping rings.
The clamping rings each include a plurality of centering screws allowing accurate positioning of the clamping rings on the shaft to be turned and with the clamping rings so fixed, the clamshell assembly also becomes centered relative to the shaft to be turned, thereby dramatically reducing the overall set-up time before the shaft turning operation can ensue. In the case of the present invention compared to my earlier arrangement, the set-up time has been cut in half----from about 2 hours to 1 hour. Also, the man hours required has been reduced from about 4 to 1.
To allow turning of the shaft all the way to its end, with my improved invention, the pair of clamping rings can be located on the shaft with a relatively close spacing therebetween allowing the clamshell assembly to be cantilevered on the ends of the glide rods outboard of one of the clamping rings.